Direct electrochemistry and electrocatalysis of hemoglobin immobilized in TiO2 nanotube films

Titanium oxide nanotubes (TiO2-NTs) synthesized by the hydrothermal method had been prepared as the co-immobilization matrix to incorporate hemoglobin (Hb) successfully. The nanostructures of TiO2-NTs were investigated by X-ray diffraction and high-resolution electron microscopy. The Hb immobilized in TiO2-NTs had a similar structure to the native of Hb and retained its near-native conformations as characterized by the UV–vis and FT-IR spectroscopy. A couple of quasi-reversible redox peaks with a formal potential of −0.34 V (vs. SCE) in 0.10 M pH 7.0 phosphate buffered saline (PBS) were observed. The amperometric response of the immobilized Hb linearly to H2O2 concentration ranged from 4 μM to 64 μM with a detection limit of 4.637 × 10−6 M and the high stability of the immobilized Hb in TiO2-NTs constituted a promising platform for the development of biosensors.